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Eye research An international team of researchers has identified 24 new genes linked to short-sightedness.

The discovery may one day help with the development of new treatments for a condition that affects billions of people around the world.

The meta-analysis of genetic data from more than 46,000 individuals is published today by the Consortium for Refraction and Myopia (CREAM) in Nature Genetics.

"The ten-fold increased risk of myopia for those carrying the highest number of risk alleles shows the clinical significance of our findings," the authors write.

The researchers analysed genetic information from individuals of European ancestry and Asian ancestry separately, then combined the data to look for similarities and differences in the genes associated with myopia.

They identified 16 genetic regions associated with myopia among the European cohort, eight of which were also identified in the Asian cohort, as well as eight additional regions when all the data were combined.

"The substantial overlap in genetic loci for refractive error between individuals of European ancestry and Asians provides evidence for shared genetic risk factors between the populations," the authors write.

A complex condition

The genes identified in the meta-analysis correspond to a broad range of functions within the eye, says Associate Professor Paul Baird from the Centre for Eye Research Australia, at the University of Melbourne.

"One of the interesting ones was involved in retinoic acid metabolism, which is found in the retina, so [that relates to] the turnover of your retinal cells and the biochemistry behind those," says Baird, one of the researchers involved in the project.

Other genes included one that plays a role in the extracellular structure of the eye, and genes involved in eye development and neurotransmission.

"So it gives you an idea that there are multiple pathways rather than just one which means that refractive errors and myopia are very complex," he says.

The findings advance understanding of the development of myopia and may in future allow doctors to predict with far greater accuracy who is likely to develop the condition, Baird says.

"If we can actually pinpoint some pathways that seem to be very important, there may be avenues where we can actually tweak genes in those pathways so we can either block them or enhance them."

The genes discovered in the study only account for 3.4 per cent of the variation in myopia, meaning there are still a huge number of unexplored factors - genetic and environmental - that contribute to development of the condition.